Liquid fuel heater for motor vehicle



Dec.3,1968 ST M ETAL 3,413,968

LIQUID FUEL HEATER FOR MOTOR VEHICLE Filed Nov 14, 1966 2 Sheets-Sheet 1In ven tor: [QGZ/VffUMP AND I qif/meo-uu/emvrwzz Dec. 3, 1 968 s M ET AL3,413,968

' LI UID FUEL HEATER FOR MOTOR VEHICLE Filed Nov. 14, 1966 2 Sheets-Sheet ln ventor;

United States Patent 3,413,968 LIQUID FUEL HEATER FOR MOTOR VEHICLEEugen Stump, Stuttgart-Unterturckheim, and Gerhard- Jiirgen Frtinkle,Gruubach, Germany, assignors to Suddeutsche Kuhlerfabrik Julius Fr.Behr, Stuttgart-Feuerbach, Germany Filed Nov. '14, 1966, Ser. No.593,815

Claims priority, application Germany, Nov. 20, 1965,

5 Claims. (Cl. 126-116) ABSTRACT OF THE DISCLOSURE Liquid fuel heaterfor heating motor vehicles or preheating engines which comprises aburner having a pressure spraying nozzle and an air nozzle around theburner, where the burner tube is surrounded by an inner chimney, anouter chimney and a heat exchanger as well as an inlet and an outlet forthe medium to be heated, which is normally air, and in which the flameis directed in a manner that it will not contact cold parts of the heatexchanger, which is achieved by the concentric arrangement of thecomponents which extend the length of the path of the flame so that theheated gases release heat to the exchanger only where the flame iscompletely burnt out.

Background of the invention The present invention relates to liquid fueloperated heaters. More in particular the invention concerns extraneousheaters for motor vehicles that burn liquid fuel and which comprise aburner, a flame chimney and a heat exchanger.

Heaters of this type are preferred for heating motor vehicles and, ifdesired, also for preheating engines. This purpose calls, on the onehand, for a small volume of structure and on the other hand, for greatheat efliciency.

In spite of the small over-all dimensions required for such a heater, itis necessary that the flame length that is obtained be as great aspossible to provide for good combustion. At the same time the flameshould not come in contact with cold wall portions, as that results inincomplete combustion. This is essentially the result of the type offuel composition, which, in turn, is determined by the limited spaceconditions. Small length of the combustion chamber permits only smallflame lengths, if flame contact with cold parts of the combustionchamber is to be avoided. Also, fuel atomization or vaporization cannotbe employed with combustion chambers of small diameter, because the jetof fuel causes fuel deposits on the cold wall of the combustion chamberpreventing complete combustion, and that results in poor fuel efficiencyand in the formation of soot.

Summary of the invention It is an object of the invention to improve theignition response in liquid fuel heaters of the type mentioned above, toincrease the burning efficiency of the fuel and to construct the heatexchanger in a manner that the above mentioned shortcomings may beavoided.

In accordance with the invention the problem is solved in that thecombustion chamber is defined by a first inner flame chimney whichconcentrically encloses the air nozzle, that a second outer flamechimney having a closed end surface encompasses the inner flame chimney,and that the flame chimney is thermally separated and insulated withrespect to the concentric heat exchanger that surrounds it.

Due to the form of construction in accordance with the invention it isaccomplished that also with crowded construction of the heater arelatively long burner flame can be obtained, which is diverted by meansof the flame 3,413,968 Patented Dec. 3, 1968 chimneys so that the flamecomes in contact only with heated flame chimneys. The concentricarrangement of the flame chimneys and of the heat exchanger, moreover,effects symmetric guidance or conduction of the gas.

-A particularly efiicient degree of operation of the heat exchanger isobtained if in accordance with a further concept of the invention theseparation between the heating gases and the medium to be heated is bymeans of a fluted chimney or cylinder. The increase of the heat transfersurface obtained thereby provides for particularly advantageous use ofthe thermal contents of the heating gases. Due to the thermally spacedand insulated arrangement of the flame chimney with respect to the heatexchanger it is accomplished that the flame chimneys do not contact themedium to be heated, so that they can maintain the operating heat thatis required for the forming of a long or extended burner flame while thedeposit of soot is avoided.

The medium to be heated is preferably conducted radially to the heatexchanger and picked up by a further radial stub. For conducting themedium on the one hand and the heating gases on the other hand, it isadvantageous if the fluted cylinder is provided at its end withstar-shaped closure baflles.

The symmetric conduction of the gas by the concentric arrangement of theflame chimney is advantageously supported in that the waste gas releasestub is arranged centrally of the heat exchanger.

A particularly eflicient heater is obtained in accordance with theinvention by the use of a burner having a pressure atomizer. In a burnerof the pressure atomizer type eflicient fuel utilization and faultlessignition conditions are obtained owing to the intimate mixing of the airof combustion and the fuel. As compared to known atomized or vaporizedfuel burners the additional advantage is obtained that the ignition in apressure atomizer takes place efiiciently also at relatively low ambienttemperatures.

In order to insure suflicient supply of air of combustion at the outerparts of the burner cone also with a relatively large angular spread ofthe fuel spray, a further feature of the invention provides auxiliaryair mixture slots at the air entrance side of the air nozzle. Due to thedifference in pressure existing between the air nozzle and the burnerchamber, the air of combustion enters the combustion chamber throughthese slots that are preferably radially disposed, while flowing on theoutside around the central air nozzle and seizing the outer fumes of thefuel spray.

It is also possible to insert a twisting element in the air nozzleopening of the burner chamber in a known manner, which increases thewhirling of the fuel spray and causes more intimate mixing with the airof combustion.

A particularly compact form of construction is obtained if, inaccordance with a further development of the invention, the fuel pump isarranged by way of a fixed coupling on the shaft of the blower that ispreferably driven by an electric motor.

If in accordance with a further advantageous feature of the inventionthe annular plate carrying the heat exchanger is arranged on thesupporting plate of the flame chimney and readily dismountable by meansof screws or the like, then simple access to and cleaning facility forthe heat exchanger is obtained.

Brief description of the drawings Further objects and advantages of theinvention will become apparent from the following specification withreference to the drawings which illustrate an embodiment of theinvention, and in which:

FIG. 1 is a longitudinal section through a heater in accordance with theinvention,

3 FIG. 2 is a section taken along the line B-B in FIG. 1, and

FIG. 3 is a section taken along the line A-A in FIG. 1.

Description of the preferred embodiment of the invention In theembodiment illustrated in FIG. 1 an inner flame chimney 2 in the form ofa hollow cylinder of steel sheet metal is arranged upon a supportplate 1. An outer flame chimney 5 is concentrically secured to thisinner flame chimney 2 by means of struts 3 and 4. This flame chimney hasa closed end 6.

An annular plate 8 or ring, which is readily dismountable, is secured tothe support plate 1 by means of screws 7 and carries the heat exchanger.The heat exchanger comprises an outer housing 9 and a fluted chimney 18.The fluted chimney 10 is provided at its end proximate the burner withas tar-shaped baffle 11 and at the end remote from the burner with asimilar baffle 12. The heat absorbing medium is supplied to the hollowspace by means of a supply socket 13 and is removed or discharged by wayof socket 14 after being heated.

Centrally of the heat exchanger a tubular stub 15 for the waste gases isprovided, which in the embodiment shown is in the form of an elbow.

The support plate 1 carries on its opposite side the burner assemblywhich is supported by means of screws 16. This assembly comprises on theone hand the air nozzle 17 having an outlet opening 18 and a whirling ortwisting member 19. The pressure spraying nozzle 20 is securedpreferably for axial displacement in the air nozzle 17. The supply ofthe fuel is by way of the fuel conduit 21. Furthermore an axiallydisplaceable ignition electrode 22 is provided. The burner device inaddition comprises the housing 23 for the blower in which anelectromotor 24 is arranged, which has a shaft 25 that carries on theone hand the blower 26, and on the other hand is connected with the fuelpump 28 by way of a coupling 27.

In order to achieve favorable admixture with the air of combustion alsoin the areas of the burner cone, the invention provides as a furtherfeature slots 29 for auxiliary air in the air nozzle 17. In theembodiment shown these slots extend radially; however, they may also bearranged obliquely. The difference in pressure that exists between theinner space of the air nozzle 17 and the combustion chamber permits exitof the air of combustion, which then flows in the combustion chamberaxially and concentrically with respect to the air nozzle 17. In thismanner it is avoided that the outer parts of the burner cone formdeposits of soot on the adjacent parts of the inner flame chimney thatcould be caused by insuflicient combustion due to lack of air ofcombustion.

The device in accordance with the invention operates in the followingmanner: The pressurized atomizing nozzle 20 is supplied with the liquidfuel by means of a conduit 21, and the air of combustion is forced intothe air nozzle 17 by means of the blower 26. The air of combustion flowsaround the central nozzle 20. The fuel spray which passes through theaperture 18 and which is intimately mixed with air of combustion isignited by the ignition electrode 22. The flame which develops extendsin axial direction inside the flame chimney 2 and is diverted by thefront end 6 of the outer flame chimney in the opposite direction. Due tothe separate and insulated arrangement of the flame chimneys 2 and 5with respect to the heat exchanger it is accomplished that the flamechimneys are not in contact with the medium that absorbs the heat, sothat their walls can be constantly maintained at the most favorabletemperature for the flame formation.

In accordance with the invention the outer flame chimney 5 is shorterthan the inner flame chimney 2 so that at the end proximate the burnerthe waste gases are enabled to enter the heat exchanger. The heatabsorbing medium, air, gas, or water for example, is introduced throughthe socket 13. The heat transfer between the waste gases and the heatabsorbing medium takes place by way of the fluted chimney 10, whichowing to its large surface makes possible a particularly favorableexploitation of the heat. The waste gases then flow forwardly in axialdirection and are discharged through the waste gas discharging tube 15.The heated medium leaves the heat exchanger by way of the socket 14.

It is apparent from the foregoing description that the burner chamberand the heat exchanger in the heater in accordance with the inventionare functionally and structurally completely separated, so thatparticularly when a pressurized fuel atomizer is used as the burner,eflicient exploitation of a long burner flame is made possible incombination with compacted contruction of the apparatus.

The invention is not limited to the embodiment illustrated anddescribed. It encompasses all advantageous partial and sub-combinationsof the features disclosed and, furthermore, structural modifications ofdetails of the heater by the man skilled in the art. We, therefore, donot wish to be limited to the embodiment illustrated, but what we desireto protect by Letters Patent of the United States is set forth in theappended claims.

We claim:

1. Heater burning liquid fuel, particularly extraneous heater for motorvehicles, comprising a burner arranged in a burner chamber and includinga fuel nozzle, an air nozzle, a whirling member disposed within said airnozzle with a space therebetween and having an aperture adjacent saidfuel nozzle, a flame chimney and a heat exchanger, said burner chambercomprising a first, inner chimney disposed around and concentric withsaid air nozzle and having an open end remote from said air nozzle, asecond outer chimney disposed around said inner chimney and having aclosed end opposite said open end of said inner chimney and remote fromsaid burner, said heat exchanger being disposed concentrically with saidinner and said outer chimney and being thermally separated and insulatedwith respect thereto.

2. Heater in accordance with claim 1, including stelliform closurebaffles at the ends of said fluted chimney.

3. Heater in accordance with claim 1, including a waste gas dischargeduct element disposed centrally and endwise of said heat exchangerremote from said burner.

4. Heater in accordance with claim 1, where said air nozzle is providedwith slots at its lower end permitting the entrance of air proximate thebase of said nozzle.

5. Heater in accordance with claim 1 including a first annular membersupporting said inner and outer chimneys, a second annular membersupported on said first annular member and supporting said heatexchanger and a third member secured to said first annular member at theside opposite from said second annular member and supporting said airnozzle, said fuel nozzle, 2. motor, a pump and a blower.

References Cited UNITED STATES PATENTS 11/1947 Jensen et al. 126997/1953 Holthouse et al.

